In an alternate timeline, Lieutenant Dexter was a human male who, by 2408 had for at least three years served as second in command of Federation Starbase 86. As a hypochondriac, he was constantly inquiring about the health of his commanding officer, Admiral William T. Riker.
He had a remarkable memory and was extremely efficient at his job, often having already completed necessary tasks before Riker had even ordered him to do so. He was also a bit of a snoop, even reading Riker's personal communications. (TNG novel: Imzadi)